There are a wide variety of machine tools and machining operations based on relative orbital motion between a tool and a workpiece. A typical, exemplary case arises in the procedure known as total form machining, wherein an abrasive tool is formed to a shape which, with allowances for the orbital offset, conforms to the shape desired in a workpiece. The tool is slowly advanced into the workpiece while orbiting, and a machining fluid is passed substantially continuously between the tool and workpiece to facilitate the work, to remove debris, to cool the tool and workpiece, and the like. Other relative motions are prevented.
By the use of such procedures, extremely complex and even delicate shapes can be attained. Other such procedures include electrical discharge machining, electro-chemical grinding, and combinations, either sequentially or in multifunctional singular operations, of a variety of such techniques. With a proper selection of materials, tool configurations, and other variables, these procedures can produce machined shapes not attainable in any other practical way and produce a level of finish and accuracy which are exceptional.
The methods and mechanisms currently employed to produce the orbital motion of the tool in relation to the workpiece is at current one of the predominant limitations on such equipment and operations. The simplest and most reliable drives, as well as the least expensive, generally employ a fixed orbit which is not variable or controllable, and which has limited accuracy. As the orbit drive mechanisms have been made more accurate, variable and/or controllable, they have also become more complex, more expensive, more fragile, and more difficult to maintain and calibrate.